1. Field of the Invention
This invention relates to the preservation of petroleum products and like substances in storage, and more particularly to the inhibition of the action of micro-organisms on petroleum and other materials subject to metabolism by micro-organisms present in the water layer in vessels and in storage tanks.
2. Description of the Prior Art
In petroleum product storage and handling facilities, such as storage tanks, pipelines, fuel lines and other equipment, petroleum products often may be in contact with water containing micro-organisms. This is particularly true in the case in oil storage tanks where a water layer usually is provided in the bottom of the tank to insure against loss by leakage, the water being replenished as necessary. Micro-organisms such as bacteria, yeast, molds, actinomyces, etc., generally are present in such tank bottom water, the organisms usually being a type which functions most effectively in the interface between the stored material and water to metabolize the hydrocarbons or constituents thereof. This metabolism not only results in loss of petroleum material but in the case of refined products it is also undesirable in other respects in that it commonly causes discoloration of the product, formation of hydrogen sulfide and undesirable gummy substances, formation of peroxides which effect the oxidation susceptibility of the petroleum product, and formation of many other undesirable compounds, such as acids. Discoloration in the case of light colored petroleum products is highly undesirable and in some cases, as with so-called white distillates or kerosene fractions, the discoloration can be so severe as to require re-refining of the product. Where additives are present in the petroleum, as is usually the case with gasoline and lubricating oils, the formation of gummy substances may represent loss of such additives or undesirable conversion thereof. Obviously, such microbial activity also is harmful to the tank structure as well since such tanks usually are formed of metal.
In the prior art, it is known to inhibit the growth of micro-organisms present in water to contact with petroleum products by means of a biocide, usually added to the water phase. Although such water phase biocides are available and have been used for controlling the growth of micro-organisms in storage tanks, their use is not feasible under conditons where access to the water phase is impractical, as in wing tanks of airplanes and in fuel lines. In such situations a hydrocarbon phase biocide is desirable. However, it is important that any such materials added to a petroleum fraction or product should not adversely affect its properties. This is particularly essential when the petroleum material is a refined or finished product.
Previously suggested hydrocarbon phase biocides are cyclic imines described in coassigned U.S. Pat. No. 3,628,926 and N-alkyl-substituted-1,3-propane-diamines in coassigned U.S. Pat. No. 3,719,458.